Spray drier apparatus



May 10, 1949.

Filed June 14 194 J. M. HALL.

SPRAY DRIER APPARATUS 2 Sheets-Sheet 1 May 10, 1949. J. M. HALL 2,469,553

' SPRAY DRIER APPARATUS Filed June 14, 1943 2 Sheets-:Sheet 2 IN V EN TOR.

6 Jose /211411421 Patented May 10, 1949 SPRAY DRIER APPARATUS Joseph M. Hall, Chicago, 111., assignor to Drying & Concentrating Company, a corporation of Delaware Application June 14', 1943, Serial No.'49o,7z9

8 Claims. 1

This invention relates to an apparatus for and a method of dehydrating liquid products.

One of the objects of the invention is the provision of a new and improved system of dehydration in which comparatively dry steam at low pressure is caused to circulate in a single dehydrating chamber for dehydrating a liquid product sprayed into said chamber.

Another object of the invention is the provision of a new and improved dehydrating chamber having novel means for recirculating the drying medium within the chamber. v

A further object of the invention is the provision of a new and improved method for dehydratin a liquid product ina single continuous I operation.

Another object of the invention is the provision of a new and improved dehydrating chamber within which the drying medium is heated and circulated for dehydrating a liquid product discharged therein. I

Another object of the invention is the provision of a new and improved dehydrating chamber having means whereby the entire dehydrating operation is performed within a-single chamber, including the heating ofthe drying medium.

A further object of the invention is the provision of a new and improved system that is simple in construction, composed of few parts, comparatively inexpensive to install, and thatfis eilicient in operation.

Other and further objects and advantages of the invention will appear from the following description, taken in connection with the accompanying drawings in which I Fig. 1 is an elevation of the dehydrating system, shown ,more or less diagrammatically;

Fig. 2 is a plan view of an upper portion of the same, with parts broken away;

Fig. 3 is an enlarged view of the heating, spraying and circulatingassemblies, with parts broken away and parts in section;

Fig. 4 is a view similar to Fi 3, but showing a modified form of construction;

Fig. 5 is a perspective view of a portion of the spray head or fan, with parts in section and parts omitted for the sake of clearness;

Fig. 6 is a section on the line 6--5 of Fig. 5; and Fig. '7 is a section on the line 1-1 of Fig. 5. It is common practice, in the dehydrating art,

to employ mechanism for concentrating and dehydrating liquid products in a plurality of stages.

, It is also conventional to heat the drying 'medium at points without the concentrating or dehydrating chamber, and to conduct the heated medium to the concentrating chamber in either an open or closed circuit. Such systems necessitate the use or an apparatus that is moreor less complicated and requires a plurality of dehydrating chambers and separate heating mechanism. 1

The present invention seeks to concentrate and simplify the construction, and to provide a system in which the drying medium is steam that is generated in a single drying chamber and recirculated within such chamber, together with means for continually removing excess steam or vapor from the system and for maintaining a partial vacuum within the dehydrating chamber. I 1

Referring now to the drawing,-the reference character III designates adehydrating'system; the

, essential features of which comprise a dehydrating chamber ll' having mounted on itsupper portion a heating assembly l2 for heating the drying medium, a. circulating assembly 'for recirculating the drying medium l3 within the dehydrating chamber, a spraying assembly It for sprayingthe liquid product in the dehydrating chamber; an exhaust fan or vacuum pump 15, operated by a motor 20, for maintaining the interior of the' dehydrating chamber at areduced atmospheric pressure, a reservoir l5 containing the? liquid product to be evaporated, and a pump I'I for supplying the liquid product to the dehydrating chamber. V 1 1 The dehydrating chamber has an'u'pper cylindrical portion it, a lower tapered portion 19, and a lower tapered extension 2 l. The upperportion of the chamber is provided 'witha top'wall or closure 22 which may incline upwardly toward the axis of the chamber. It is provided withjan axial openin 23 over which is mounted a cylindrical heating assembly comprising a casingf24, havinga top wall 25 which is providedwithja restricted axial opening 26 through which 1vapor evaporated from the liquid productjis conducted, as will presently appear. iMouhtedonthQside and top of the casing 24 are a'pluralityor electricalheating units 21, 28, torfheating,the recirculated vapor or drying medium, aswill presentlybe described. Other electrical heating. units J29 are mounted on the top wall' 22 'of the dehydrator adjacent to the heatingassemblyjmemberju. These heating elements createa heating z'orie within and adjacent to the casin through which the drying medium is causedjto circulate during the operation of the'apparatus for'sup'erheating such medium. f Suitable means are providedjforjcausing"the recirculation of the drying fm'edium @within, the

dehydrating chamber ".1 shown, lthis'assem 3 bly l3 comprises a cylindrical, tubular, directing or guide member 3|, having its upper portion return bent in a eurve,.as at 32. and with its lower edge attached to the lower edge of the tubular member 3|, thus forming a double wall enclosing an annular space 300 tapering downwardly. It will thus be seen that the upper edge of the guide member 3| is a. smooth curve between which and the side walls of the casing 24 an annular passage 50 is provided through which the drying medium is adapted to flow.

Suitable means are also provided for causing the vapor generated in the chamber id to flow upwardly through the cylindrical chamber 3 I As shown, this is accomplished by the spray member, which also functions as a fan, as will now be described. The spray assembly comprises a shaft 33 extending downwardly axially through the cylindrical member 3|, and constitutes an elongation of the armature shaft of the motor 34 mounted above the heating assembly member 24. This shaft is surrounded and protected by a casing 35, which is connected to a conical deflector 36, which in turn is connected with the casing of the motor 34.

Attached to the lower end of the shaft 33, and rotatable therewith, is a cast steel spray head or hub 31, which is hollow and has integral therewith vanes or blades 38 extending outwardly therefrom. These vanes 38 are flattened and, with the head 31, form a fan for recirculating the drying medium within the dehydrating chamber A tube 38" for the liquid product extends along the leading edge of each vane or blade, and is secured in the head and welded to the vane for conducting the liquid product from the head to the nozzles 4|. These nozzles are detachably connected to the outer ends of the corresponding tubes. In order that the flow of drying medium through the fan shall be uniform throughout the diameter of the fan, the blades 38 are made to taper in width toward their outer ends, and the angle of the blade faces to the horizontal is greater at their inner than at their outer portions. The difference in width and angularity compensates for the difierent speeds of these portions.

The armature shaft 33 is hollow, and a pipe 42 is in communication therewith for conducting the liquid product from the reservoir 6 to the spray head. The liquid product may be delivered to the spray head by means of a pump 43, operated by a motor 44, as is usual in such constructions. The arms 38 of the spray are in the form of fan blades which are adapted to direct the vapor or drying medium upwardly through the cylindrical member 3| and, due to the restricted opening 26, cause a greater portion of the drying medium to be directed downwardly between the casing 24 and .the directing or guide member 3|.

In order to cause the drying medium to rotate in its downward movement, the cylindrical directing or guide member 3| is provided on its outer surface with inclined or spiral vanes 45, which are rigidly attached to the return bent wall 32 of the cylindrical member 3|. These vanes are also attached at their outer edges to the wall of the casing 24 for holding the parts in assembled relation.

It is desirable that the pressure within the chamber be .below atmosphere in order to accelerate the evaporation of the sprayed particles. An exhaust fan l5, operated by a motor for lowering the pressure in the dehydrating chamber and for exhausting excess steam therefrom, is provided' for this purpose. Theintake of this fan is in communication, through a pipe 46, with a snail or chamber 41 surrounding the coneshaped -member or shield 36 and over the restricted opening 26, as shown more clearly in Fig. 3 of the drawing. The pipe 46 is attached tangentially to the chamber 41 in such a manner as to cause the exhaust vapor to rotate in the same direction as in the dehydrating chamber ll, so as to avoid turbulence. The pipe 46 may be provided with an adjustable valve for controlling the proportionate amount of steam exhausted through the pipe 46.

In the operation of the device, the liquid product is pumped from the reservoir l3 and delivered to the spray head 31, which is rotated by the motor 34, and this rotation sprays the liquid product into the upper portion of the dehydrator chamber, as indicated in Fig. 1 of the drawing. After the apparatus has been nmning a few minutes practically all of the air will have been re- 7 placed by steam or vapor evaporated from the product, and the drying medium will then be entirely vapor or steam. This steam will be caused to move upwardly through the axial passage of the guide member 3|, and a portion of the steam will be exhausted by the fan l6 through the passage 26, and the remainder and larger portion of the steam will pass over the upper end of the tubular member 3| and downwardly between the vanes 45, which will cause the air to rotate and move across the nozzles 4| for dehydrating the liquid product.

In passing upwardly through the tubular member 3|, and then downwardly through the passage 50, the vapor will have its temperature very much increased as it passes through this heated zone of the chamber, and will move downwardly in an outer spiral adjacent the side walls of the chamber, and then reverse and flow upwardly in the same spiral direction in an inner spiral up to the tubular member 3|, thus completing its cycle of movement. The fan- I5 is operated at such velocity, and is of such capacity, and the valve 40 adjusted to such a. position, that the pressure within the chamber is maintained below atmospheric.

The nature of the productto be dehydrated, and the percentage of moisture to be left in the dehydrated product, will determine, to a large extent, the most efficient conditions to be maintained within the dehydrator chamber during the dehydrating operation.

It has been found in evaporating milk, for instance, that the reduction of the pressure to about 10" of mercury, and with the drying medium at F., substantially the same results are obtained as heating the medium to 240 F. and

operating at atmospheric pressure. Satisfactory the medium has cooled below the temperature at which the dehydrated particles would be injured.

The lower portion of the chamber may be, and preferably is, provided adjacent the tapered portion 2| with a directing cylinder 43, having a shield 48 surrounding the member 43, both of which are coaxial with the chamber and supported in any suitable manner, as by means of arms or brackets 49. The shield 43" terminates wardlygas at operation of the a, a my, Qngthe dehydrating chamas usual 'in' such constructions.

le rotating valve .jl, operated by a mbenisithe ame as in the congs.l ran 3, but the liquid 1 6 ,is ,delivered to what under pressure by a 11 eaydrating.q

9 of ,the ubiilar member 3| ngihent -oftlie axles 45 is substantiall'ylt :slthatpr risly described. The header 62 is mounted in the'upper portion of the space 30c} between-the inner and outer walls of the tubular member 3 I, and has a plurality of depending brancheonduits 6} each of which is provided with a nozzle '6! extending outwardly below the outer wan G'Fof th mei nber 3 I The inner cylindrical wall 66 of the tubular directing beIiJ3PL ZQXtIIGCddownwardly yond the outer curved wall 61, and is flared outp 68, below the nozzles SI, for directing the-gaseous drying medium outwardly. The 'lower; edge'o'f 'the outer wall-69 of the guide member 3'l -jis also flaredoutwardly for directing the dry; gfirfnediumacross the ends'of the nozzles 6|.

13y means otthisarrangement the liquid product being forced --radially-outwardly through the nozzles $51 ,is broken-up into' very fine particles, and"these-particlesare dehydrated by the rotating column org-ax;drying'jmedium which, in the present instance, is vapor or dry steam at high temperature lw press e.'. 'The steam is re*- circ atedbymeans of" afan"B5,which is secured to the lower end of the motor shaft 33', within but adjacent to the upper end of the member 3|. The operation of the device is similar to that already described, and it is not thought necessary to repeat the same.

It will thus be seen that the drying medium is heated within the dehydrating chamber, and that it is recirculated within said chamber. The drying medium is derived from the moisture evaporated from the liquid product and is superheated in the heating zone and preferably maintained at sub-atmospheric pressure during the device. The temperature and pressure may each be adjusted to meet the requirements of any particular product that is being dehydrated.

It is thought from the foregoing, taken in connection with the accompanying drawings, that the construction and operation of my devlcewill be apparent to those skilled in the art, and that changes in size, shape, be made ,without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a dehydrating system, a dehydrating chamber, a'heating zone in the upper portion of said chamber, means for heating said zone, means for circulating and recirculating a drying medium in saidchamber through said zone, said means comprising a tubular guide member arranged axially of said chamber in the upper portion thereof within said zone, angularly arranged baf fies on the exterior of said member for causing the medium moving down across the same to move downwardly within said chamber in an outer immediately below spiral, a rotating spray head said member for spraying said product into the downwardly moving drying medium, fan blades carried by said head for causing said downwardly;

flowing medium to reverse and flow in an inner spiral upwardly through said member over the top thereof and then downwardly externally thereof through said heating zone, and means for exhausting vapor extracted from said product and for reducing the atmospheric pressure within said chamber.

2. A dehydrating chamber comprising an upper cylindrical portion, a lower tapered portion, said cylindrical portion having a top wall with an axial opening therethrough, a casing over said opening, a tubular member extending into said opening and spaced downwardly and inwardly from said casing, a nozzle'head rotatably mounted just below said member and having arms in the form of fan blades with nozzles on the outer ends of said arms for spraying a liquid product into said chamber and for causing the recirculation of a drying medium upwardly through said member and downwardly between said member and casingand across said nozzles, means on said member for causing said medium to flow downwardly in an outer spiral, and-means for superheating said medium as it is recirculated within said chamber just prior to its passage across said nozzles.

3. A combined fan and distributor member comprising a hollow head member for receiving a liquid product to be dehydrated, vanes extending radially therefrom, tubu1ar members along the leading edge of each vane, and aspray nozzle at the end of each tubular member, said vanes tapering in width toward their outer ends and having their side faces at a greater angle to the horizontal at their inner ends than at their outer ends, whereby the velocity of the air flowing through the fan is uniform throughout the diameter of the fan.

4. In a dehydrating system, a dehydrating chamber, a heating zone in the upper portion of said chamber, means for heating said zone, means for circulating and recirculating a drying medium in said chamber through said zone, said means comprising a tubular guide member arranged axially of said chamber in the upper portion thereof within said zone, means including baffles for causing the drying medium that moves upwardly through the guide member and through the heating zone to be thereafter directed downwardly in an outer spiral, a rotating spray head immediately below said member for spraying said product into the downwardly moving drying proportion and detail may medium, fan blades carried by said head for causing said downwardly flowing medium to reverse and flow in an inner spiral upwardly through said member over the top thereof and then downwardly externally thereof through said heating zone, andmeans for exhausting vapor extracted from said product.

5. -A dehydrating chamber comprising an upper cylindrical portion, a lower tapered portion, said cylindrical portion having a top wall with an .ed just below said member and having arms in p the form of fan blades with nozzles .on the outer ends of said arms for sprayinga liquid product into said chamber and for causing the recirculation 0 a drying medium upwardly through said mem r and downwardly between said member and casing and across said nozzles, and means for heating said medium as it is recirculated within the chamber and baflles for imparting to the thus heated medium a downward spiral motion immediately prior to its passage across said nozzle.

6. In a system for dehydrating a material, a dehydrating chamber of circular cross section with smooth interior side walls and normally containing only said material and vapor derived therefrom, means including a tubular guide member, a fan and stationary deflector blades, all mounted in the central upper portion of said chamber to force vapor derived from said material in a stream extending centrally upwardly and subsequently extending outwardly towardthe side walls of 'the chamber in a spiral manner thereby providing a closed pathof vapor circulation in the chamber, a heat transfer zone located entirely within the central upper portion of the chamber and including heat exchange surfaces for heating the vapor prior to said outward flow,

' means for supplying heat to said heat transfer surfaces, and means to spray said material centrally outwardly into said. stream in that portion thereof wherein the vapor is moving in a down ward spiral path.

7. In a system for dehydrating a material, a

dehydrating :chamber of circular cross section.

entirely within the central upper portion of the chamber and including heat exchange surfaces for heating the vapor prior to said outward flow, means for supplying heat to said heat transfer surfaces, means to spray saidmaterial centrally outwardly into said stream in that portion thereof wherein the vapor is moving in a downward spiral path, and means for diverting and exhausting from the chamber a sufficient portion of the stream to maintain a sub-atmospheric pressure in the chamber.

8. In a system for dehydrating a material, a dehydrating chamber of circular cross section with smooth interior side walls and normally containing only said material and vapor derived therefrom, means including a tubular guide member, a fan and stationary deflector blades, all mounted in the central upper portion of said chamber to force vapor derived from said material in a stream extending centrally upwardly and subsequently extending outwardly toward the side walls of the chamber in a spiral manner thereby providing a closed path of vapor circulation in thechamber, a heat transfer zone located entirely within the central upper portion of the .chamber and including heat exchange surfaces for heating the vapor prior to said outward flow,

means for supplying heat to said heat transfer surfaces, means to spray said materially centrally outwardly into said stream in that portion thereof wherein the vapor is moving in a downward spiral path, and means for diverting and exhausting from the chamber a sufllcient portion of the stream to maintain a sub-atmospheric pressure in the chamber, said last named means including an exhaust duct secured to and emerging from the chamber ata point above the tubular guide member.

JOSEPH M. HALL.

, file of this patent:

with smooth interior side walls and normally contaming only said material and vapor derived therefrom, means including a tubular guide member, a fan and stationary deflector blades, all mounted in thecentral upper section of said chamber to force vapor derived from said mate rial in a stream extending centrally upwardly and subsequently extending outwardly toward the side walls of the chamber in'a spiral manner thereby providing a closed path of vapor circulation in the chamber, a heat transfer-zone located UNITED STATES PATENTS OTHER REFERENCES Principles of Chemical Engineering, Walker, McGraw-Hill Book Co. (3d

ed., 1937), New York.

Certificate of Correction Patent No. 2,469,553. May 10, 1949. JOSEPH M. HALL It is hereby certified that error appears in the printed specification 0f the above numbered patent requiring correction as follows:

Column 7, line 53, claim 7, for the word section read portion; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 18th day of October, A. D. 1949.

[SEAL] THOMAS F. MURPHY,

Assistant Uommissi ner of Patents. 

